A couple who became violently ill after eating fish bought from a popular fish market have warned others about a little-known toxin lurking unnoticed in some of the seafood sold across Australia.
The Queensland pair were left experiencing bizarre symptoms after purchasing “some delicious cod” from the Mooloolaba Fish Market, Sunshine Coast, on August 9 and consuming it over three consecutive meals.
They said one of the strange symptoms was cold water feeling boiling hot to the touch.
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“Unfortunately, my partner and I have since been diagnosed with Ciguatera Fish Poisoning (CFP),” Lee Jee said in a post to the public on Facebook.
The couple experienced fatigue, muscle and joint aches, stomach discomfort and what the man described as “some extremely strange nerve symptoms” after eating the fish.
“Ordinary cold tap water can feel like an ice burn, and even holding a cold metal object can become painful,” he said.
“Then there’s the itching.
“No rash, no lumps — just relentless itching in bizarre places like our hands, knees, shins and feet.”
The man said the couple had been unaware of CFP before falling sick.
“This is mainly a heads-up for anyone else who, like us, had never heard of ciguatera,” he said.
No way to spot contaminated fish
The couple’s warning comes as Queensland Health confirms nine reported cases of ciguatera poisoning across the state so far this year.
Over the past 10 years, from 2016 to 2025, Queensland averaged 16 reported cases per year.
Worldwide, an estimated 50,000 to 500,000 people are affected annually.
CFP is a form of food poisoning caused by eating warm-water ocean fish carrying ciguatoxin.
And the toxin is particularly insidious because there is no obvious way to detect it before eating the fish.
“Ciguatera toxin does not affect the appearance, smell or taste of fish, and there is no known food preparation method that can remove it from a fish,” a Queensland Health spokesperson said.
“Anyone can be affected by ciguatera poisoning.”
The strange reaction to cold the couple experienced is one of the most distinctive symptoms of ciguatera.
The toxin is produced by tiny marine organisms called dinoflagellates, which are a type of microscopic algae.
Small fish consume the organism, and the toxin can then build up through the food chain as larger fish eat those smaller fish.
It can become more concentrated as it moves up the food chain, which is why Queensland Health advises against eating large warm-water ocean fish.
Some high-risk fish are no-take species in Queensland, including Chinamanfish, red bass and paddletail.
Other species that can carry ciguatera toxins include coral trout, Spanish mackerel, red emperor, coral cod, wrasse, trevally, surgeon fish and yellowtail kingfish.
The symptoms can sound almost impossible
People who have experienced the poisoning have described unusual initial and, in some cases, persistent neurological effects.
Cold water can feel boiling hot. Skin can feel badly sunburnt when there is no visible burn. Feet can get itchy.
Some people have reported the bizarre hot-cold reversal lasting more than two years, while one woman reportedly experienced cold water feeling hot for 18 months.
Queensland Health said alcohol, coffee, tea and even eating fish, meat or nuts can trigger neurological symptoms again in some people.
One person said their mouth tingled and swelled after drinking wine, while another reported a relative could still not drink alcohol without the soles of their feet itching, 35 years after contracting ciguatera.
Others have described tingling or numbness around the mouth, hands and feet, alongside vomiting, diarrhoea, abdominal pain, muscle and joint pain, severe itching, dizziness and weakness.
And then there is the strange sensation your teeth are about to fall out. It is a recognised neurological symptom of ciguatera poisoning, despite the teeth themselves not actually becoming loose.
These are individual accounts from people describing their experiences with ciguatera, and do not mean everyone who contracts the poisoning will experience the same symptoms.
Researcher injected toxin into her own arm
University of Queensland (UQ) researcher Professor Irina Vetter has spent years investigating how the toxin affects the nervous system, particularly the bizarre way it can make normally harmless cold temperatures feel unpleasant or painful.
Her research found ciguatoxins appear to preferentially activate nerves normally signalling cold, shifting the threshold of cold sensitivity so even an otherwise harmless cool temperature feels unpleasant or even burning.
Vetter has even personally injected a tiny amount of ciguatoxin into her arm as part of her research.
“It caused a burning sensation, local redness, and exposure to cool temperatures was unpleasant,” she said.
Vetter declined to elaborate further on the experience, saying “people can be a bit sensitive about these sorts of experiments”.
Her team previously published research examining how ciguatoxins activate specific cold-pain pathways and produce burning pain from cooling.
An unlikely cancer connection
The findings could also have implications for understanding and treating neurological side effects associated with cancer treatment.
“Because some cancer patients, specifically those treated with a chemotherapy drug called oxaliplatin, experience the same symptoms where innocuous cool becomes unpleasantly painful,” Vetter said.
“If we can understand how ciguatera causes these symptoms at a molecular level, this might give insight into how the chemotherapy drug does it, and this will help develop targeted treatments.”
Vetter said the ultimate goal was to find better treatments for both ciguatera and the neurological side effects associated with cancer drugs.
“A successful outcome would be development of treatments that are based on the molecular mechanisms,” she said.
“This could involve re-purposing drugs that are used for other conditions, or new drug development.”
And while the symptoms can be bizarre and, for some people, persistent, Vetter said there was an important message for anyone worried they may have eaten contaminated fish.
“Probably that it is likely to be transient, and that most people recover,” she said.
How to reduce the risk
An old fisherman’s myth shared online suggests if a cat refuses to eat a piece of the fish you’re unsure about, you shouldn’t eat it either, but there is no evidence the trick can detect ciguatoxin.
Queensland Health recommends taking the following precautions when eating warm-water ocean fish:
- Avoid the head, roe, liver and other internal organs, where the toxin is concentrated.
- Avoid large warm-water fish and limit the whole weight to around six kilograms per fish.
- When eating a warm-water ocean fish for the first time, eat no more than 300 grams.
- If ciguatera-like symptoms develop, stop eating the fish and see your doctor.
- Do not mix fillets from different species of large warm-water fish.
- Do not catch fish from known ciguatera areas.
- Never eat unidentified fish you have caught yourself.
What to do if you think you’ve eaten contaminated fish
If your lips, tongue or fingers begin tingling or going numb after eating warm-water fish, or cold water suddenly feels burning hot, stop eating the fish and seek medical advice, Queensland Health advises.
Symptoms can begin within hours and may include nausea, vomiting, diarrhoea, itching, muscle and joint pain, dizziness and weakness.
For the Queensland couple, the experience has left them with a new caution around what lands on their dinner plate.
“It’s definitely something I’ll be thinking about before choosing a large reef fish again.”
7NEWS.com.au contacted Mooloolaba Fish Market seeking comment, but no response was received.
